A CBCT (Cone Beam Computed Tomography) is known which reconstructs a three-dimensional CT data of an imaging target on the basis of a plurality of transmission images imaged by using a cone X-ray irradiated to the imaging target from a radiation source which is turned around the imaging target. In such a CBCT, the three-dimensional CT data can be prepared in a short time without turning the radiation source a plurality of times. It is desired to prepare the three-dimensional CT data that exhibits a more suitable view field.
A radiotherapy is known in which a patient is treated by irradiating therapeutic radiation to a tumor affected region. A radiotherapy apparatus contains an imager system for imaging transmission images of the patient lying on a couch; and a therapeutic radiation irradiating unit for irradiating the therapeutic radiation to the patient. The radiotherapy apparatus is desired to be cheaper in manufacturing cost and longer in life.
“DEVELOPMENT OF A FOUR-DIMENSIONAL IMAGE-GUIDED RADIOTHERAPY SYSTEM WITH A GIMBALED X-RAY HEAD” discloses a technique of checking a position of tumor with a therapeutic beam by use of EPID (Electronic Portal Imaging Device).
In JP 2003-522576A, a cone beam computer tomography system is disclosed which contains a flat panel imager for imaging transmission images by using an X-ray beam which has transmitted through the object while turning around an object, and reconstructs a three-dimensional CT data on the basis of the transmission images. The cone beam computer tomography system can change the size of a view field of the three-dimensional CT data by changing a position of the flat panel imager with respect to an X-ray source that emits the X-ray beam.
Japanese Patent No. 3,785,136 discloses a radiotherapy apparatus that can easily design a therapy plan after the radiotherapy is performed on a specimen. The radiotherapy apparatus contains a radiation irradiating head for irradiating therapeutic radiation; an image processing section for generating an image of an affected region of the specimen to which the therapeutic radiation is irradiated from the radiation irradiation head; and a control unit for controlling the radiation irradiating head and the image processing section so that a period is repeated which includes the generation for the image and irradiation of the therapeutic radiation, and prior to the irradiation of the therapeutic radiation in a first period, the imaging of the image is completed in which a diagnostic X-ray in a second period next to the first period is used, and processing of the imaged image is completed in the irradiation of the therapeutic radiation in the first period, and the image of the affected region is generated.